It is not safe to give Atarax (hydroxyzine) to a 1.5-month-old baby without a pediatrician's direct prescription. Crying is a very common reaction after a DPT injection due to mild soreness or a low-grade fever. To help soothe your little one, you can try holding them close and applying a cool, damp cloth gently to the injection site. If your baby seems in pain or develops a fever, please contact your pediatrician, who can prescribe a safe, weight-appropriate dose of infant paracetamol. Please consult your doctor before administering any medication.